202 Proceedings of the Royal Physical Society. 



The ore fused with the greatest facility, and 100 lbs. would 

 be capable of furnishing about 70 lbs. of bichromate of potash. 

 We have just received analysis of three specimens of the 

 ore made in the Laboratory of the Cleveland Steel Works, 

 1884, which gave : 



Sesquioxide of Chromium, . . 37-18 3879 2.5-50 per cent. 



Protoxide of Iron, . . . -"^ "-^ oo.ii ^c.^ri 



Protoxide of Manganese, 



Silica, ..... 



Sulphur, ..... 



Phosphoric Acid, 



Lime. ...... 



III. — TOMNADASHAN. 



1. Topography. — The small hamlets of Tomnadashan and 

 Easter TuUich are situated on the sloping hillside, which 

 rises somewhat steeply from the southern shore of Loch Tay, 

 about 2 miles north-eastward from the village of Ardeonaig, 

 and 7| miles S.W. from Kenmore. 



Copper ore was discovered here by the late Marquis of 

 Breadalbane, who, after mining and dressing it, had it 

 smelted in works erected on the shore of the loch. 



2. Geology. — The neighbouring country is almost entirely 

 composed of nearly flat hydromica schists, with zones of 

 limestone, hornblende rock, and grit, and is traversed by 

 numerous dykes of basalt, porphyrite, and felsite, which 

 serve to enliven the otherwise rather monotonous geological 

 picture of the region. 



At Tomnadashan the schists are pierced by a boss of 

 crystalline rock, which has produced a certain amount of 

 contact metamorphism around its edges. The metamorphic 

 strata are baked and crumpled, and occasionally penetrated 

 by offshoots or " apophyses " from the intrusive mass, in 

 which fragments of the schist are sometimes completely 

 enveloped. 



The rock resembles ordinary grey dolerite externally, but 

 microscopic examination shows that it is quite different from 

 the true dolerites found in the long Tertiary dykes of the 

 vicinity. It is granular throughout, quite free from green 



